Crusher and clearance indicator



May 22, 1962 B. B. BURBANK CRUSHER AND CLEARANCE INDICATOR 3 Sheets-Sheet 1 Filed Feb. 18, 1959 Flai 4 2 jf 413 ATTORNEYS.

May 22, 1962 B. B. BURBANK 3,035,782

CRUSHER AND CLEARANCE INDICATOR Filed Feb. 18, 1959 3 Sheets-Sheet 2 INVENTOR.

BWM; @l

A TTORNE YS.

May 22, 1962 Filed Feb. 18, 1959 B. B. BURBANK CRUSHER AND CLEARANCE INDICATOR 60 (Y(LE FHA 5 E CONYEHTEN Z PHAfE F//YS T AMPLIFIER 5 Sheets-Sheet 3 INVENTOR.

BWM/ @ul ATTORNEYS.

3,035,782 CRUSHER AND CLEARANCE INDICATOR Benjamin B. Burbank, Brunswick, Maine, assigner to Bath Iron Werl-rs Corporation, Bath, Maine, a corporation of Maine Filed Feb. 18, 1959, Ser. No. 794,069 2 Claims. (Cl. 241--89) This invention relates to crushers, and more particullarly concerns crushers of the rotating type which are adjustable as to distance between the rotating hammers and the crushing elements, and with means for yautomatically measuring and controlling said distance.

The distance between the rotating hammers and the crushing elements in a crusher is important because -this distance governs the product size produced by the crusher. Product size is important because it is usually the specilication upon which the material is sold or governs its use in further processing. In the case of coal crushing, product size is very important to the etliciency of coke ovens, furnaces or coal red steam plants. With some materials, particularly coal, moisture in the material fed to the :crusher will alter the productivity of it or its finished product size. Experience gained by years of processing such materials of variable moisture content have resulted in information enabling operators to adjust the clearance of a crusher by definite amounts to compensate for known moisture variations. This is a compromise between production capacity and product size within workable limits. Such adjustments have to be made and necessitate shutdowns of the crusher or ytime consuming trial `and error adjustments -to arrive at the clearance which will give optimum conditons of greatest eiiiciency.

Many materials crushed to reduce particle size are desired in several nished product sizes so that it may be necessary to shutdown and adjust the clearance of a crusher to meet demands for these various sizes. A crusher therefore may operate a few hours or a few days producing a finished product of one size and then shift to another, all from the same raw material feed. To accomplish this the raw material supply must be temporarily stopped, the machine shutdown and reset, or if done by the trial and error method of adjustment, several tons of off-size product will result.

Through normal use the hammers and the crushing elements of crushers wear so that the distance therebetween changes. The result is a gradual change of tinished product size. Adjustments have to be frequently made to compensate for this natural wear for which there is no indication except the gradual product size change.

To correct the conditions mentioned it is highly impractical if not impossible, to measure in the field the clearance distance between rotating hammers and crushing elements without shutdown. lt requires considerable time to shutdown a crus-her and measure the clearance, then reset it. Generally, it is a highly disagreeable and dirty job involving considerable expense. Such shutdowns `are extremely unwelcome because many crushers are expected to run twenty-four hours a day for days at a time. Crushers are often one element in a long train ot' interrelated machinery, all of which must be shutdown it' the crusher is shutdown.

Accordingly, it is an object of lthis invention to provide a crusher which overcomes the heretofore mentioned problems,

it is another object of this invention v.to provide a crusher with means for automatically indicating that a predetermined optimum size of product is being obtained, and for so indicating during the continual operation of the crusher.

It is another object of .this invention to provide a nited States Patent C crusher which is adjustable -to give optimum performance under varying conditions of moisture of the feed material, rate of feed of the material, land of product size desired.

It is another object of this invention to provide a crusher with means for indicating the elect that wear of the elements of the crusher has on optimum product size.

Itis another object of the invention to provide a crusher with means for accurately controlling the product size, which means does not obstruct unduly the ow of material through a crusher.

It is another object of this invention to provide means for accurately indicating the product size during the time that the product is being formed in the crusher, which means continues to give accurate information even though the elements of the machine are subject to wear.

It is another object of this invention to provide a means lfor accurately and quickly changing from one product size to another desired size without interruption of ilow of material through the crusher or shutdown thereof.

It is another object to provide a crusher with means for automatically following a signal to keep the elements of the crusher in proper, predetermined spaced relationship.

It is another object of this invention to provide a means of remote indication and control of the clearance of a crusher and thereby enable an operator at a remotely located point to control product size of crushers. Such means is desirable when crushing a radio-active material in isolated buildings temporarily restricted against personnel entry.

*It is another object to provide a crusher with means for determining how evenly the crushing elements thereof wear. v

Other objects and advantages of this invention, including its simplicity and economy, as well as the ease with which it may be adapted to existing equipment, will further become -apparent hereinafter and in the drawings, in which:

FIG. l is a sectional view in front elevation of a crusher constructed in accordance with this invention;

FIG. 2 is a view in cross section of the crusher of FIG. l, taken as indicated by the lines and arrows II-ll vwhich. appear in FG. l;

FiG. 3 is an enlarged view of the probe which forms an element of this invention and also shows the electrical circuit connected to the magnetic probe;

FIG. 4 is a View of the magnetic probe of FIGS. 2 and 3 looking in the direction of the arrows iV-IV;

FIG. 5 is a partial view of another embodiment of magnetic probe;

"1G 6 is a partial view of another embodiment of magnetic probe; and

FG. 7 is a View of a magnetic probe including automatic means for controlling its position.

Although specific terms are used in the following description `for clarity, these terms are intended to refer only to the structure shown in the drawings and are not intended to define or limit the scope of the invention.

Turning now to the specific embodiments of the invention selected for illustration in the drawings, there is shown a crusher for coal, ore, and the like, which crusher is provided with a frame 11 which has formed at the top thereof a feed hopper 12, and which has rotatably mounted therein a hammer rotor 13. Hammer rotor 13 is provided with Ihammers 14, and the material fed into hopper 12 is struck by the rotating hammers 14 as part of the crushing process. The material is then delivered at high speed to the crushing elements 15 and are swept past or through screen fbars 16 into a delivery chute 17 which is positioned below hammer rotor 13. As the hammers 14 rotate they define a hammer circle 3 18 and the distance 'between hammer circle 18 and the face of breaker elements is important as is hereinafter more fully explained.

A magnetic probe is provided vfor accurately ascertaining the distance between hammer circle 18 and the face of breaker elements 15. The magnetic probe includes magnetic sensing means 21 which is mounted on crushing elements 15 and is movable therewith. A magnetic field 22 extends inwardly from sensing means 21 and rotating hammers 14 traverse magnetic field 22 to generate an electric current in a coil 23 which is positioned around a magnet 24 of sensing means 21. Electrical leads 25 extend from coil 23 to electrical indicating means 26. Electrical indicating means 26 may be a r'nilliammeter (the current may be preampliiiedif desired), and the meter 26 is calibrated to show the distance 4between harnmer circle 18 and crushing elements 15. indicating means 25 may also be calibrated and related to product size and moisture content of the feed material. In this illustration, clearance adjustment compensation is accomplished manually.

An alarm system is provided which is electrically connected to indicating means 26 and acautated thereby to opearte a visual alarm 27 and an audio alarm 28 when the clearance between the hammers and the face of the breaker element is improper and such that the product size will be outside a predetermined range. Also connected in the circuit is a control box 29 which may be manually adjustable to actuate the alarms at desired voltage or current.

Additionally, there is provided a follow-up system 31 in the embodiment of FIG. 7, which operates in response to the signal received from sensing means 21 to maintain a predetermined distance between hammer circle .13 and crushing elements 15.

Crushing elements 15 include upper breaker blocks 32 and lower breaker blocks 33 which are adjustable as to distance from hammer circle 18 by jack bolts 34 and 35. Jack nbolts 34 and 35 move the breaker blocks 32, 33 around pivot pins 36, 37 which are mounted on frame 11.

Referring to FiG. 3, the magnetic sensing means 21 includes the magnetized bars 38, 39 and the encasing shield bars 42, 43 which are made of a non-magnetic material, preferably brass, which prevent loss of magnetism to the breaker block 33 with its adjacent screen bars 16 by rigid isolation, and which also `physically protect the magnetized fbar 39 from being damaged by the hard material being passed through the screen bars. This prevents deflection of the magnet which would cause error in the readings of the clearance indicator 26. The magnetic sensing means 21 is constructed of material that wears evenly with adjacent surfaces and thus provides a true clearance indication as crushing element wear progresses.

Referring to the alternative embodiment of the magnetic probe shown in FIG. 6, the number 24a indicates a magnetic bar which is positioned in a slot in lower breaker block 33 with encasing shield bars 42a and 43a interposed therebetween. At the youter end of magnet 24a there is provided a coil 23a and a pair of electrical leads 25a which are connected to the electrical indicating means. Surrounding this coil 23a and contacting mag- .netically the end or magnet 24a Vis a pole cap 41 of magnetic material which completes the magnetic path from magnet 24a to the breaker 33 and 'bar 16. This increases the intensity of the magnetic lines of force 22 at the opposite end. VAt the other end of magnet 24a there is provided a replaceable tip 44 Which includes a magnetic or magnetized bar 45 and encasing shield Ibars 46, 47. The magnetic tip 44 wears with the breaker block 33 and is replaceable with replacement of the breaker block. This arrangement is of advantage in that the main section of the magnetic sensing means, which includes the magnet 24a, is thus protected Vfrom damage and from wear.

V31, which is illustrated in FIG. 7 is as follows.

Referring to FIG. 5, the magnetic sensing unit is embodied in screen bars or a breaker block of a nonmagnetic material such as lil-14% manganese steel or austenitic stainless steels which are frequently used in the manufacture of Crushers for special purposes. FIG. 5 shows a magnet 24J), a coil 23b and electrical leads 2511 which are connected to an indicating means. Magnetic blocks 43 and 49, slightly larger than the poles of magnet 24h, are tightly fitted between the non-magnetic screen -bars 15 and 16 and welded. They may be inserted in holes in a solid breaker block and welded in place if desired. Magnet 24h rests upon these blocks and creates a magnetic fiel-d 22 that extends into the hammer circle 18. There is no necessity to shield the probe blocks 4S and 49 because the surrounding bars 15 and 16 are non-magnetic and no leakage occurs.

Referring to FIG. 7, the magnetic sensing means 21 has electrical leads 25e extending therefrom which connect with a vfirst amplifier 52 which is Vconnected in circuit with a clearance indicator V53, a manually adjustable Vnull point bridge 54, a `second amplifier 55, a phase converter 56 and a vservo motor 57. The phase converter 56 is connected to a single phase, 60 cycle, A.C. supply, and servo motor V57 is connected to gearing 53 to actuate jack bolt 35, which positions the screen bars 16 and breaker block 33.

In operation, the magnetic field of force 22 extends into the crusher past the hammer circle 18 into the path ofthe moving hammers 14. Field 22 is an intense magnetic field which is generated by the strong permanent magnets as shown in the drawing. As the hammers 14 traverse the extended `magnetic field 22, they cause fiuctuations of .intensity ofthe magnetic field which pass through the -coil windings 23, thereby inducing an alternating current.

The intensity of this alternating current is governed by the degree to which themoving hammers 14 traverse the 'field 220i magnetic force. The closer the hammers 14 are to the magnetic sensing means 21, the greater the current produced. The amount of current is therefore related to the clearance or spacing between the rotating hammers 14 and the magnetic sensing means 21, and the amount of the clearance or spacing is indicated on indicating means 26 to which the current impulse is transmitted via an amplifier.

The operation of automatic adjusting (servo) system The current generated by magnetic sensing means 21 is transmitted byelectrical conductors 25e as a signal voltage to first amplifier 52. This signal voltage is proportionate to the clearance between the rotating hammers 18 and lower breaker block 33. The signal voltage is amplified at the first amplifier and is indicated on the clearance indicator 53.

Also the output of first amplifier 52 is fed to a bridge 54 which is manually adjusted by a control knob to give a null point or zero voltage which is fed to the second amplifier 55. Should the distance vary between the rotating hammers 14 and lower breaker block 33 after this zero or null point is established, then the magnetic sensing means 21 feeds a greater or smaller voltage to first amplier 52. Theoutput of amplifier 52 (being proportionately different) unbalances the bridge 54 so as to send a proportionate signal from bridge 54 to amplifier 55. This signal is amplified and fed to servo motor 57.

Second amplifier is also fed one phase of a two phase, 60 cycle, A.C. supply, this phase being 90 degrees out of phase with the other phase from the same supply which is also fed to servo motor 57. This degree phase difference creates a condition whereby a decrease of signal strength from magnetic sensing means 21 results in servo motor 57 rotating one way, and whereby an increase of signal strength from magnetic sensing means 21 results in rotation of servo motor 57 in the opposite direction. In this manner, the distance between rotating hammers 14 and lower breaker block 33 is maintained constant, the motor 57 rotating screw 58 to change clearance and re-establish balance.

By manually adjusting null point bridge 54, any desired clearance between hammers 14 and block 33 is obtained, and the automatic adjusting (servo) system 31 maintains that clearance until bridge 54 is manually reset. Servo motor 57 normally does not rotate, but only rotates when magnetic sensing means 21 sends in a signal greater or smaller than a predetermined value. When this happens, servo motor 57 rotates until the ditlerence in signal is balanced out.

First amplifier 52 may be any standard electronic amplier, such as a or 20 watt audio amplier, nul point bridge 54 is basically a Wheatstone bridge, second amplilier 55 may be any standard heavy duty electronic circuit using vacuum tubes, or it may be a magnetic amplifier, phase converter 56 may be a standard unit involving capacitors or other means which displace the phases by 90 degrees, and servo motor 57 may be a standard unit available in many sizes and operating voltages.

It is to be noted -that magnetic sensing means 21 is preferably located at the pinch point between hammer circle 18 and the block 33, that is, the closest point between the hammer circle 18 and the surface of block 33.

Magnetic sensing means 21 is so constructed as to not obstruct unduly the ow of material through the slots between screen bars 16 (see FIG. 4).

The end of the magnet 24 wears with the surface of block 33 and the surface of screen bar 16, and wears at `the same rate so that the distance between hammer circle 18 and the end of magnet 24 is substantially the same as the distance between the hammer circle 18 and the face of block 33 and of screen bars 16.

lWhile permanent magnets are shown in the drawings, it is realized that an electro-magnet could be substituted therefor.

The encasing shields give good support to the magnetic bars, physically protect the magnetic bars from damage, act as a mechanical spacer, and magnetically isolate the magnetic bars.

It is to be noted that in the circuit of FIG. 3, the amount of clearance is indicated on indicating means 26, and additionally, visual alarm 27 and audio alarm 28 are actuated when the clearance falls outside a predetermined range. These alarms act as a signal to the operator who is then in a position to manualy aldjust jack screws 35 to bring the clearance back to within the desired range.

Permanent magnets are preferred because of simplicity, and powerful permanent magnets, such as Alnico, an alloy of aluminum, nicked and cobalt, have proved very satisfactory. Y

It is to be noted that the apparatus of this invention is easily adjustable to existing equipment. In addition to indicating the clearance on a meter, the signal from magnetic sensing means 21 may be fed into a recorder to give a continuous record during a period of time, if such a record is desired. The apparatus measures and indicates wear of both moving parts and stationary parts, thus enabling operator to correct or compensate for this Wear without shutdown of the machine, and also enables the operator to change the clearance at will without shutdown of the machine. The follow-up servo system 31 maintains the clearance at a constant ligure and thus insures a constant product size.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred embodiment. Various changes may be made in the shape,

size and arrangement of parts. For example, equivalent elements may be substituted for those illustrated and described herein, parts may be reversed, and certain features of the invention may be utilized independently of the use of other features, all without departing from the spirit or scope of the invention as defined in the subjoined claims. In addition, the invention may be installed in both the upper and lower crushing elements and in other types of crushers including the conventional one-way and reversible hammermill types.

Having thus described my invention, I claim:

1. A crusher for coal and the like, said crusher comprising; a frame; anvil elements mounted on said frame and dening a crushing chamber, at least a lower one of said anvil elements being adjustable; a rotor mounted for rotation within said chamber; a plurality of hammers of magnetic material extending from said rotor, the extremities of said hammers during rotation of said rotor defining a hammer circle within said chamber; voltage generating means comprising a permanent magnet and a winding, said permanent magnet being mounted for adjustment with said adjustable lower anvil element, said permanent magnet being provided with at least one pole piece magnetically insulated from said adjustable lower anvil element, said pole piece extending inward to the edge of said chamber, the spacing between the extremity of said pole piece and said hammer circle having a relationship to the spacing between the surface of said adjustable lower anvil element and said hammer circle, said permanent magnet and pole piece establishing a magnetic tield which extends into said hammer circle, said winding being coupled to said permanent magnet in Xed coupling relation thereto for generating in said winding, as a result of the rapid movement of said hammers through said magnetic ield, a peak voltage which is dependent upon the spacing between the surface of said adjustable lower anvil and said hammer circle.

2. Apparatus as claimed in claim 1 characterized in that said permanent magnet is provided with a second pole piece which abuts against the rearward surface of said adjustable lower anvil element.

References Cited in the lle of this patent UNITED STATES PATENTS 2,340,609 Mestas Feb. 1, 1944 2,359,158 Rushing Sept. 26, 1944 2,401,175 Morrill May 28, 1946 2,548,599 Garr Apr. l0, 1951 2,575,710 Hardigg Nov. 20, 1951 2,661,160 Keiper Dec. 1, 1953 2,888,211 Myers May 2.6, 1959 

